Laser -
In the case of the image you were trying to post, you copied the URL for the product*. To get to just the picture, you need to click the "Zoom" button on that page, and then you can right-click on the picture and "copy image URL" (this in the Chrome browser). The image's URL is: http://assets.rockler.com/media/catalog/product/cache/1/image/720x720/9df78eab33525d08d6e5fb8d27136e95/2/7/27237-01-1000.jpg Note that it ends in ".jpg". An image on the net will most likely end in ".jpg", ".gif", or ".png" When you see this at the end of your link, you've got the right link.
To post the picture, click on the tree (the "Insert Photo" link) above, and enter the image URL.
*You can use the chain link image (insert
link) to provide a shortcut to the page. So, instead of the long link you have above, you could just have "
Rockler 3-piece Engineer Square Set"